Organic electroluminescent device

ABSTRACT

The present disclosure provides an organic electroluminescent device including: an anode; a cathode; and one or more organic material layers interposed between the anode and cathode and selected from the group consisting of a hole injection layer, a hole transporting layer, a light emitting layer, an electron transporting layer, and an electron injection layer, and further including a lifetime enhancement layer (LEL) between the light emitting layer and the electron transporting layer.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/KR2014/012888 filed Dec. 26, 2014, claiming priority based on KoreanPatent Application Nos. 10-2013-0166103 filed Dec. 27, 2013 and10-2014-0158154 filed Nov. 13, 2014, the contents of all of which areincorporated herein by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates to an organic electroluminescent deviceincluding one or more organic material layers.

BACKGROUND ART

Studies on an organic electroluminescent (EL) device have continued toblue electric light emission using an anthracene single crystal in 1965,and then an organic electroluminescent device having a two-layerlaminated structure, which is composed of a hole layer (NPB) and a lightemitting layer (Alq₃), was proposed by Tang in 1987. Since then, theorganic electroluminescent device has been proposed in the form of amultilayer-laminated structure which imparts each characteristic andsubdivided function, such as an organic layer which is responsible forinjecting and transporting holes, an organic layer which is responsiblefor injecting and transporting electrons, and an organic layer whichinduces electroluminescence to occur due to the combination of holes andelectrons in the device in order to implement high efficiency and longlifetime characteristics required for commercialization. Theintroduction of a multilayer-laminated structure improved theperformance of the organic electroluminescent device to the level ofcommercialization characteristics, thereby expanding the applicationrange of the multilayer-laminated structure from the start of a radiodisplay product for a vehicle in 1997 to a mobile information displaydevice and a display device for TV.

The demand for enlargement and high resolution of a display imposeschallenges of high efficiency and long lifetime on an organicelectroluminescent device. In particular, the high resolutionimplemented by forming a larger number of pixels in the same area incursa result of decreasing the light emitting area of the organicelectroluminescent pixel, thereby reducing the lifetime, which hasbecome the most important technical challenge which the organicelectroluminescent device needs to overcome.

In the organic electroluminescent device, when current or voltage isapplied to two electrodes, holes are injected into an organic materiallayer at the anode, and electrons are injected into an organic materiallayer at the cathode. When the injected holes and electrons meet eachother, an exciton is formed, and the exciton falls down to a bottomstate to emit light. In this case, the organic electroluminescent devicemay be classified into a fluorescent electroluminescent device in whichsinglet excitons contribute to light emission and a phosphorescentelectroluminescent device in which triplet excitons contribute to lightemission according to the type of electron spin of the excitons formed.

In the electron spins of the excitons formed by recombining electronsand holes, the singlet exciton and the triplet exciton are produced at aratio of 25% and 75%. In the fluorescent electroluminescent device inwhich light is emitted by singlet excitons, it is impossible for theinternal quantum efficiency to theoretically exceed 25% according to theproduction ratio, and the external quantum efficiency of 5% is acceptedas the limitation. In the phosphorescent electroluminescent device inwhich light is emitted by triplet excitons, when a metal complexcompound including a transition metal heavy atom such as Ir and Pt isused as a phosphorescent dopant, the light emitting efficiency may beimproved up to 4 times compared to the fluorescent electroluminescentdevice.

As described above, the phosphorescent electroluminescent deviceexhibits higher efficiency in terms of light emitting efficiency thanthe fluorescent electroluminescent device based on theoretical facts,but in a blue phosphorescent device except for green and redphosphorescent devices, the development level for the color purity ofthe deep blue color, a phosphorescent dopant with high efficiency, and ahost with a wide energy gap, which satisfies the requirements, is sominimal that the blue phosphorescent device has not been commercializedup to now, and a blue fluorescent device is used for products.

In order to improve characteristics of the organic electroluminescentdevice, study results for enhancing stability of the device bypreventing holes from diffusing into an electron transferring layer havebeen reported. There has been proposed a technology in which a materialsuch as BCP or BPhen is used between a light emitting layer and anelectron transferring layer to prevent holes from diffusing into theelectron transferring layer, and a probability of recombining holes andelectrons is effectively increased by limiting the diffusion into theinside of the light emitting layer. However, in derivatives such as BCPor BPhen, oxidation stability for holes deteriorates and durability forheat is weak, and accordingly, the lifetime of the organicelectroluminescent device is decreased, and the commercialization is notachieved. Further, these materials simply serve to block holes and thusinhibit electrons from moving, thereby increasing the driving voltage ofthe organic electroluminescent device.

DISCLOSURE Technical Problem

The present disclosure has been made in an effort to solve theaforementioned problems, and an object thereof is to provide an organicelectroluminescent device having high efficiency, a low voltage, and along lifetime.

Technical Solution

The present disclosure provides an organic electroluminescent deviceincluding: an anode; a cathode; and one or more organic material layersinterposed between the anode and the cathode and selected from the groupconsisting of an electron injection layer, an electron transportinglayer, a light emitting layer, an electron transporting layer, and anelectron injection layer, and further including a lifetime enhancementlayer (LEL) between the light emitting layer and the electrontransporting layer.

Here, the lifetime enhancement layer (LEL) includes a bipolar compoundhaving both an electron withdrawal group (EWG) with a high electronabsorption property and an electron donor group (EDG) with a highelectron donor property, in which the bipolar compound satisfies all ofthe following (a) to (d) conditions.

(a) an ionization potential [Ip(LEL)] is 5.5 eV or more,

(b) E_(HOMO)−E_(LUMO)>2.9 eV,

(c) triplet energy is 2.3 eV or more, and

(d) ΔEst<0.5 eV (ΔEst indicates a difference between singlet energy andtriplet energy of the compound)

BRIEF OF DRAWINGS

FIG. 1 is a cross-sectional view illustrating an organicelectroluminescent device according to an exemplary embodiment of thepresent disclosure.

[Description of Main Reference Numerals of Drawings] 100: Anode 200:Cathode 301: Hole injection layer 302: Hole transporting layer 303:Light emitting layer 304: Lifetime enhancement layer 305: Electrontransporting layer 306: Electron injection layer

BEST MODE

Hereinafter, the present disclosure will be described.

The present disclosure relates to an organic electroluminescent deviceincluding: an anode; a cathode; and an organic material layer interposedbetween the anode and the cathode, in which the organic material layerincludes one or more selected from the group consisting of a holeinjection layer, a hole transporting layer, a light emitting layer, alifetime enhancement layer, an electron transporting layer, and anelectron injection layer, and the lifetime enhancement layer (LEL)includes a bipolar compound having both an electron withdrawal group(EWG) with a high electron absorption property and an electron donorgroup (EDG) with a high electron donor property. Here, the bipolarcompound may be used as a material for not only a lifetime enhancementlayer, but also an electron transporting layer, an electron injectionlayer, or all these layers.

Hereinafter, the present disclosure will be described as follows withreference to FIG. 1.

In the organic electroluminescent device according to the presentdisclosure, an anode 100 serves to inject holes into an organic materiallayer 300.

A material which constitutes the anode 100 is not particularly limited,and materials typically known in the art may be used. Non-limitingexamples thereof include: a metal, such as vanadium, chromium, copper,zinc, and gold; alloys thereof; a metal oxide, such as zinc oxide,indium oxide, indium tin oxide (no), and indium zinc oxide (IZO); acombination of metal and oxide, such as ZnO:Al or SnO₂:Sb; a conductivepolymer, such as polythiophene, poly(3-methylthiophene),poly[3,4-(ethylene-1,2-dioxy)thiophene] (PEDT), polypyrrole, andpolyaniline; carbon black, and the like.

A method for preparing the anode 100 is also not particularly limited,and the anode 100 may be prepared by methods typically known in the art.Examples thereof include a method for coating an anode material on asubstrate composed of a silicon wafer, quartz, a glass plate, a metalplate, or a plastic film.

In the organic electroluminescent device according to the presentdisclosure, a cathode 200 serves to inject electrons into the organicmaterial layer 300.

A material which constitutes the cathode 200 is not particularlylimited, and materials typically known in the art may be used.Non-limiting examples thereof include: a metal, such as magnesium,calcium, sodium, potassium, titanium, indium, yttrium, lithium,gadolinium, aluminum, silver, tin, and lead; alloys thereof; and amultilayer structured material such as LiF/Al and LiO₂/Al.

Further, a method for preparing the cathode 200 is also not particularlylimited, and the cathode 200 may be prepared by methods typically knownin the art.

As the organic material layer 300 included in the organicelectroluminescent device according to the present disclosure, thoseused as an organic material layer of the existing organicelectroluminescent device may be used without limitation, and examplesthereof include one or more selected from the group consisting of a holeinjection layer 301, a hole transporting layer 302, a light emittinglayer 303, a lifetime enhancement layer 304, an electron transportinglayer 305, and an electron injection layer 306. In this case, inconsideration of characteristics of the organic electroluminescentdevice, it is preferred to include all of the above-described organicmaterial layers.

The hole injection layer 301 and the hole transporting layer 302, whichare included in the organic material layer 300 of the presentdisclosure, serve to transport holes injected from the anode 100 to thelight emitting layer 303. A material which constitute the hole injectionlayer 301 and the hole transporting layer 302 is not particularlylimited as long as the material has a low hole injection barrier and ahigh hole mobility, and a hole injection layer/transporting layermaterial used in the art may be used without limitation. Non-limitingexamples thereof include an arylamine derivative.

Further, the light emitting layer 303 included in the organic materiallayer 300 of the present disclosure is a layer in which holes andelectrons meet each other to form an exciton, and the color of lightwhich the organic electroluminescent device emits may vary according tothe material constituting the light emitting layer 303. The lightemitting layer 303 may include a host and a dopant, and it is preferredthat the host is included in a range of 70 to 99.9 wt %, and the dopantis included in a range of 0.1 to 30 wt %.

More specifically, in the case of a blue fluorescence, a greenfluorescence, or a red fluorescence, the light emitting layer 303 mayinclude the host in a range of 80 to 99.9 wt %, and may include thedopant in a range of 0.1 to 20 wt %. In addition, in the case of a bluefluorescence, a green fluorescence, or a red phosphorescence, the lightemitting layer 303 may include the host in a range of 70 to 99 wt %, andmay include the dopant in a range of 1 to 30 wt %.

The host included in the light emitting layer 303 is not particularlylimited as long as the host is publicly known in the art, andnon-limiting examples thereof include: an alkali metal complex compound;an alkali earth metal complex compound; or a fused aromatic ringderivative, and the like.

More specifically, as the host material, it is preferred to use analuminum complex compound, a beryllium complex compound, an anthracenederivative, a pyrene derivative, a triphenylene derivative, a carbazolederivative, a dibenzofuran derivative, a dibenzothiophene derivative, ora combination of one or more thereof, which may enhance the lightemitting efficiency and lifetime of the organic electroluminescentdevice.

Furthermore, the dopant included in the light emitting layer 303 is notparticularly limited as long as the dopant is publicly known in the art,and non-limiting examples thereof include an anthracene derivative, apyrene derivative, an arylamine derivative, a metal complex compoundincluding iridium (Ir) or platinum (Pt), and the like.

The light emitting layer 303 may be a single layer or may be composed ofa plurality of two or more layers. Here, when the light emitting layer303 is composed of a plurality of layers, the organic electroluminescentdevice may emit light with various colors. Specifically, the presentdisclosure may provide an organic electroluminescent device whichincludes a light emitting layer composed of a plurality of homogeneousmaterials between the hole transporting layer 302 and the lifetimeenhancement layer 304, or includes a light emitting layer composed ofheterogeneous materials in series to display a mixed color. Further,when the device includes a plurality of light emitting layers, thedriving voltage of the device is increased, whereas the current value inthe organic electroluminescent device becomes constant, so that it ispossible to provide an organic electroluminescent device in which thelight emitting efficiency is improved with the number of light emittinglayers

The lifetime enhancement layer 304 included in the organic materiallayer 300 according to the present disclosure is for improving thelifetime of the organic electroluminescent device, and is includedbetween the light emitting layer 303 and the electron transporting layer305.

A material, which constitutes the lifetime enhancement layer 304, is notparticularly limited, but is preferably a bipolar compound having bothan electron withdrawal group (EWG) with a high electron absorptionproperty and an electron donor group (EDG) with a high electron donorproperty.

More specifically, the bipolar compound has an ionization potential of5.5 eV or more, and may have an ionization potential of specifically ina range of 5.5 to 7.0 eV, and preferably in a range of 5.5 to 6.5 eV.

In addition, the difference (E_(HOMO)−E_(LUMO)) between a HOMO value anda LUMO value of the bipolar compound exceeds 2.9 eV, and may bespecifically in a range of more than 2.9 eV and 3.5 eV or less.

In this case, the triplet energy is 2.3 eV or more, may be specificallyin a range of 2.3 to 3.5 eV, and is preferably in a range of 2.3 to 3.0eV. Furthermore, the difference between singlet energy and tripletenergy of the bipolar compound is less than 0.5 eV, and specifically ina range of less than 0.5 eV and 0.01 eV or more.

That is, holes move with the ionization potential level in the organicelectroluminescent device, and when holes pass through the lightemitting layer 303 to diffuse or move into the electron transportinglayer 305, an irreversible decomposition reaction occurs due tooxidation, thereby leading to a decrease in lifetime of the organicelectroluminescent device.

In contrast, since the present disclosure includes the lifetimeenhancement layer 304 composed of a bipolar compound having anionization potential [Ip(LEL)] of 5.5 eV or more to prevent holes fromdiffusing or moving into the electron transporting layer 305, thelifetime of the organic electroluminescent device may be enhanced. Thatis, holes are blocked by the high energy barrier of the lifetimeenhancement layer 304 and do not diffuse or move into the electrontransporting layer 305 and remain in the light emitting layer 303.

Here, when the light emitting layer 303 is composed of a redphosphorescent material, the bipolar compound included in the lifetimeenhancement layer 304 may have an ionization potential of 5.5 eV ormore, but when the light emitting layer 303 is composed of a greenphosphorescent material or a blue phosphorescent material, the bipolarcompound has an ionization potential of preferably 6.0 eV or more.

Meanwhile, in the bipolar compound, since the difference(E_(HOMO)−E_(LUMO)) between HOMO value and LUMO value exceeds 2.9 eV,the triplet energy is 2.3 eV or more, and the difference (ΔEst) betweensinglet energy and triplet energy is less than 0.5 eV, the use of thebipolar compound for the lifetime enhancement layer 304 may preventexcitons formed in the light emitting layer 303 from diffusing into theelectron transporting layer 305, and may also suppress a phenomenon inwhich light is emitted at the interface of the light emitting layer 303and the electron transporting layer 305. As a result, this prevents thespectrum mixed color of the organic electroluminescent device, andimproves the stability, thereby improving the lifetime of the organicelectroluminescent device.

More specifically, the bipolar compound has both an electron withdrawalgroup (EWG) with a high electron absorption property and an electrondonor group (EDG) with a high electron donor property, and thus hascharacteristics in which the electron clouds of HOMO and LUMO areseparated. For this reason, the difference (ΔEst) between triplet energyand singlet energy of the compound is minimal, and thus, the compoundsatisfies the relationship of ΔEst<0.5 eV, and as a result, the compoundmay have high triplet energy (Ti) even though the difference(E_(HOMO)−E_(LUMO)) between the HOMO value and the LUMO value exceeds2.9 eV.

Here, when the light emitting layer 303 is composed of a redphosphorescent material, the bipolar compound included in the lifetimeenhancement layer 304 may have an triplet energy of 2.3 eV or more, butwhen the light emitting layer 303 is composed of a green phosphorescentmaterial, the bipolar compound has triplet energy of preferably 2.5 eVor more, or when the light emitting layer 303 is composed of a bluephosphorescent material, the bipolar compound has triplet energy ofpreferably 2.7 eV or more.

Meanwhile, when electrons and holes are unbalanced due to the differencebetween the number of holes injected from the anode 100 and the numberof electrons injected from the cathode 200, electrons or holes, whichfail to form an exciton due to recombination, are accumulated in thelight emitting layer 303. The electrons or holes accumulated in thelight emitting layer 303 prevent oxidation and reduction from smoothlyoccurring in the light emitting layer 303, or affect the adjacentlayers, thereby reducing the lifetime of the organic electroluminescentdevice.

In contrast, as the hole mobility and the electron mobility of thebipolar compound are 1×10⁻⁶ cm²/V·s or more at normal temperature, whenthe bipolar compound is used for the lifetime enhancement layer 304, thelifetime of the organic electroluminescent device may be improved bypreventing the injection of electrons from being delayed compared to thenumber of holes injected from the anode 100.

In practice, the bipolar compound included in the lifetime enhancementlayer 304 of the present disclosure exhibits the hole mobility of 1×10⁻⁶cm²/V·s or more at normal temperature due to the electron donor group(EDG), and the electron mobility of 1×10⁻⁶ cm²/V·s or more at normaltemperature due to the electron withdrawal group (EWG). Accordingly,when the bipolar compound is used for the lifetime enhancement layer304, electrons may be effectively injected into the light emitting layer303. When electrons are smoothly injected into the light emitting layer303 as described above, the efficiency of forming the exciton in thelight emitting layer 303 may be improved, thereby enhancing the lifetimeof the organic electroluminescent device.

The bipolar compound included in the lifetime enhancement layer 304 ofthe present disclosure is formed by combining a moiety having anelectron withdrawal group (EWG) characteristic with a high electronabsorption property with a moiety having an electron donor group (EDG)characteristic with a high electron donor property. In this case, thebipolar compound is characterized by including one or more electronwithdrawal group (EWG) moieties represented by the following ChemicalFormula as the electron withdrawal group (EWG).

In the formulae,

A₁ to A₁₁ are the same as or different from each other, and are eachindependently N or C(R), at least one thereof is N, and in this case, aplurality of R's is the same as or different from each other even thoughbeing equally indicated, and these groups may form a fused ring with anadjacent group. For example, in the case of a plurality of C(R)'s, A₁and A₂, A₂ and A₃, A₃ and A₄, A₄ and A₅, A₅ and A₆, or A₆ and A₁ maycombine with each other to form a fused ring, and A₇ and A₈, A₅ and A₉,A₉ and A₁₀, A₁₀ and A₁₁, and A₁₁ and A₇ may combine with each other toform a fused ring.

R is selected from the group consisting of hydrogen, deuterium, ahalogen group, a cyano group, a nitro group, an amino group, a C₁ to C₄₀alkyl group, a C₂ to C₄₀ alkenyl group, a C₂ to C₄₀ alkynyl group, a C₃to C₄₀ cycloalkyl group, a heterocycloalkyl group having 3 to 40 nuclearatoms, a C₆ to C₆₀ aryl group, a heteroaryl group having 5 to 60 nuclearatoms, a C₁ to C₄₀ alkyloxy group, a C₆ to C₆₀ aryloxy group, a C₁ toC₄₀ alkylsilyl group, a C₆ to C₆₀ arylsilyl group, a C₁ to C₄₀ alkylboron group, a C₆ to C₆₀ aryl boron group, a C₁ to C₄₀ phosphine group,a C₁ to C₄₀ phosphine oxide group, and a C₆ to C₆₀ arylamine group,

the alkyl group, the alkenyl group, the alkynyl group, the cycloalkylgroup, the heterocycloalkyl group, the aryl group, the heteroaryl group,the alkyloxy group, the aryloxy group, the alkylsilyl group, thearylsilyl group, the alkyl boron group, the aryl boron group, thephosphine group, the phosphine oxide group, and the arylamine group of Rare each independently unsubstituted or substituted with one or moreselected from the group consisting of deuterium, a halogen group, acyano group, a nitro group, an amino group, a C₁ to C₄₀ alkyl group, aC₂ to C₄₀ alkenyl group, a C₂ to C₄₀ alkynyl group, a C₃ to C₄₀cycloalkyl group, a heterocycloalkyl group having 3 to 40 nuclear atoms,a C₆ to C₄₀ aryl group, a heteroaryl group having 5 to 40 nuclear atoms,a C₁ to C₄₀ alkyloxy group, a C₆ to C₆₀ aryloxy group, a C₁ to C₄₀alkylsilyl group, a C₆ to C₆₀ arylsilyl group, a C₁ to C₄₀ alkyl borongroup, a C₆ to C₆₀ aryl boron group, a C₁ to C₄₀ phosphine group, a C₁to C₄₀ phosphine oxide group, and a C₆ to C₆₀ arylamine group, and

the electron withdrawal group (EWG) moiety is a nitrogen-containingheteroaromatic hydrocarbon having 5 or 6 nuclear atoms, in which 1 to 3carbons are substituted with nitrogen. Further, the electron withdrawalgroup moiety may be in a form in which two or more rings are simplypendant to or fused with each other, or in a form in which two or morerings are fused with an aryl group.

In the present disclosure, the electron withdrawal group (EWG) moietymay be more embodied as a structure represented by the followingchemical formulae, and is preferably a 6-membered nitrogen-containingheteroaromatic hydrocarbon including 1 to 3 nitrogens. Preferrednon-limiting examples of the electron withdrawal group (EWG) moietyinclude pyridine, pyrimidine, triazine, pyrazine, and the like.

In the present disclosure, the carbon or nitrogen atom of the moietyhaving an electron withdrawal group (EWG) characteristic with a highelectron absorption property forms a bond with the moiety having anelectron donor group (EDG) characteristic with a high electron donorproperty.

The bipolar compound included in the lifetime enhancement layer 304 ofthe present disclosure is characterized by including an electron donorgroup (EDG) moiety represented by the following Chemical Formula 1.

As a non-limiting example of the moiety having an electron donor group(EDG) characteristic with a high electron donor property as describedabove, it is possible to use a fused nitrogen-containing heteroaromaticring such as indole, carbazole, and azepine; or a fused polycyclicaromatic ring such as biphenyl, triphenylene, and fluorancene, and morespecifically, the moiety may be represented by the following ChemicalFormula 1.

In Chemical Formula 1,

X₁ is selected from the group consisting of O, S, Se, N(Ar₁),C(Ar₂)(Ar₃), and Si(Ar₄)(Ar₅),

Y₁ to Y₄ are the same as or different from each other, and are eachindependently N or C(R₁), and in this case, a plurality of R₁'s is thesame as or different from each other even though being equallyindicated, and these groups may form a fused ring with an adjacentgroup,

X₂ to X₃ are the same as or different from each other, and are eachindependently N or C(R2), and in this case, a plurality of R2's is thesame as or different from each other even though being equallyindicated, and these groups may form a fused ring with an adjacentgroup,

R₁ and R₂ and Ar₁ to Ar₅ are the same as or different from each other,and are each independently selected from the group consisting ofhydrogen, deuterium, a halogen group, a cyano group, a nitro group, anamino group, a C₁ to C₄₀ alkyl group, a C₂ to C₄₀ alkenyl group, a C₂ toC₄₀ alkynyl group, a C₃ to C₄₀ cycloalkyl group, a heterocycloalkylgroup having 3 to 40 nuclear atoms, a C₆ to C₆₀ aryl group, a heteroarylgroup having 5 to 60 nuclear atoms, a C₁ to C₄₀ alkyloxy group, a C₆ toC₆₀ aryloxy group, a C₁ to C₄₀ alkylsilyl group, a C₆ to C₆₀ arylsilylgroup, a C₁ to C₄₀ alkyl boron group, a C₆ to C₆₀ aryl boron group, a C₁to C₄₀ phosphine group, a C₁ to C₄₀ phosphine oxide group, and a C₆ toC₆₀ arylamine group, and the alkyl group, the alkenyl group, the alkynylgroup, the cycloalkyl group, the heterocycloalkyl group, the aryl group,the heteroaryl group, the alkyloxy group, the aryloxy group, thealkylsilyl group, the arylsilyl group, the alkyl boron group, the arylboron group, the phosphine group, the phosphine oxide group, and thearylamine group of R₁ and R₂ and Ar₁ to Ar₅ are each independentlyunsubstituted or substituted with one or more selected from the groupconsisting of deuterium, a halogen group, a cyano group, a nitro group,an amino group, a C₁ to C₄₀ alkyl group, a C₂ to C₄₀ alkenyl group, a C₂to C₄₀ alkynyl group, a C₃ to C₄₀ cycloalkyl group, a heterocycloalkylgroup having 3 to 40 nuclear atoms, a C₆ to C₄₀ aryl group, a heteroarylgroup having 5 to 40 nuclear atoms, a C₁ to C₄₀ alkyloxy group, a C₆ toC₆₀ aryloxy group, a C₁ to C₄₀ alkylsilyl group, a C₆ to C₆₀ arylsilylgroup, a C₁ to C₄₀ alkyl boron group, a C₆ to C₆₀ aryl boron group, a C₁to C₄₀ phosphine group, a C₁ to C₄₀ phosphine oxide group, and a C₆ toC₆₀ arylamine group.

In the present disclosure, Chemical Formula 1 may be more embodied asany one of the following A-1 to A-24. However, Chemical Formula 1 is notlimited thereto.

In A-1 to A-24,

the definitions of R₂, Y₁ to Y₄, and Ar₁ to Ar₅ are the same as those inthe above-described Chemical Formula 1. In this case, in considerationof physical and chemical characteristics of the compound, the electrondonor group (EDG) moiety is preferably A-1 to A-6.

Meanwhile, Chemical Formula 1, which is the electron donor group (EDG)moiety in the present disclosure, may be used alone as the structure ofChemical Formula 1, or may combine with the following Chemical Formula 2or Chemical Formula 3 to be represented as a fused structure.

More specifically, Y₁ to Y₄ in Chemical Formula 1 are each independentlyN or C(R₁), and when these groups are a plurality of C(R₁)'s, one of Y₁and Y₂, Y₂ and Y₃ or Y₃ and Y₄ forms a fused ring with the followingChemical Formula 2. In this case, a plurality of R₁'s may be the same asor different from each other.

Further, when both X₂ and X₃ in Chemical Formula 1 are C(R₂), aplurality of R₂'s in this case may each combine with the followingChemical Formula 2 or Chemical Formula 3 to form a fused ring.

In Chemical Formulae 2 and 3,

Y₅ to Y₁₄ are the same as or different from each other, and are eachindependently N or C(R₃), and in this case, in the case of a pluralityof C(R₃)'s, a plurality of R₃'s is the same as or different from eachother, and may combine with Chemical Formula 1 to form a fused ring, and

X₄ is the same as X₁, and in this case, a plurality of Ar₁'s to Ar₅'s isthe same as or different from each other.

A plurality of R₃'s, which does not form a fused ring, is the same as ordifferent from each other even though being equally indicated, and areeach independently selected from the group consisting of hydrogen,deuterium, a halogen group, a cyano group, a nitro group, an aminogroup, a C₁ to C₄₀ alkyl group, a C₂ to C₄₀ alkenyl group, a C₂ to C₄₀alkynyl group, a C₃ to C₄₀ cycloalkyl group, a heterocycloalkyl grouphaving 3 to 40 nuclear atoms, a C₆ to C₆₀ aryl group, a heteroaryl grouphaving 5 to 60 nuclear atoms, a C₁ to C₄₀ alkyloxy group, a C₆ to C₆₀aryloxy group, a C₁ to C₄₀ alkylsilyl group, a C₆ to C₆₀ arylsilylgroup, a C₁ to C₄₀ alkyl boron group, a C₆ to C₆₀ aryl boron group, a C₁to C₄₀ phosphine group, a C₁ to C₄₀ phosphine oxide group, and a C₆ toC₆₀ arylamine group, and

the alkyl group, the alkenyl group, the alkynyl group, the cycloalkylgroup, the heterocycloalkyl group, the aryl group, the heteroaryl group,the alkyloxy group, the aryloxy group, the alkylsilyl group, thearylsilyl group, the alkyl boron group, the aryl boron group, thephosphine group, the phosphine oxide group, and the arylamine group ofR₃ are each independently unsubstituted or substituted with one or moreselected from the group consisting of deuterium, a halogen group, acyano group, a nitro group, an amino group, a C₁ to C₄₀ alkyl group, aC₂ to C₄₀ alkenyl group, a C₂ to C₄₀ alkynyl group, a C₃ to C₄₀cycloalkyl group, a heterocycloalkyl group having 3 to 40 nuclear atoms,a C₆ to C₄₀ aryl group, a heteroaryl group having 5 to 40 nuclear atoms,a C₁ to C₄₀ alkyloxy group, a C₆ to C₆₀ aryloxy group, a C₁ to C₄₀alkylsilyl group, a C₆ to C₆₀ arylsilyl group, a C₁ to C₄₀ alkyl borongroup, a C₆ to C₆₀ aryl boron group, a C₁ to C₄₀ phosphine group, a C₁to C₄₀ phosphine oxide group, and a C₆ to C₆₀ arylamine group.

In the present disclosure, the compound formed by fusing ChemicalFormula 1 with Chemical Formula 2 may be more embodied as any one ofcompounds represented by the following Chemical Formulae 1a to 1f.

In Chemical Formulae 1a to 1f,

X₁ to X₄ and Y₁ to Y₈ are the same as those defined in Chemical Formulae1 and 2.

According to a preferred embodiment of the present disclosure, Y₁ to Y₄,which do not form a fused ring, are N or C(R₁), and it is preferred thatY₁ to Y₄ are all C(R₁), and Y₅ to Y₈ are N or C(R₃), and it is preferredthat all of Y₅ to Y₈ are C(R₃). In this case, a plurality of R₁'s andR₃'s is the same as of different from each other.

The compound of the present disclosure, in which Chemical Formula 1 isfused with Chemical Formula 2, may be embodied as any one of thefollowing Chemical Formulae B-1 to B-30. However, the compound is notlimited thereto.

In Chemical Formulae B-1 to B-30,

Ar₁ and R₁ to R₃ are the same as those defined in Chemical Formulae 1and 2.

More specifically, Ar₁ is a substituted or unsubstituted C₆ to C₄₀ arylgroup, or a substituted or unsubstituted heteroaryl group having 5 to 40nuclear atoms, and

it is preferred that R₁ to R₃ are each independently hydrogen, asubstituted or unsubstituted C₁ to C₄₀ alkyl group, a substituted orunsubstituted C₆ to C₄₀ aryl group, or a substituted or unsubstitutedheteroaryl group having 5 to 40 nuclear atoms.

Here, Chemical Formulae B-1 to B-30 having a structure in which ChemicalFormula 1 and Chemical Formula 2 are fused include one or more fusedindole or fused carbazole moieties.

Further, in the present disclosure, the compound formed by fusingChemical Formula 1 with Chemical Formula 3 may be embodied as any one ofcompounds represented by the following Chemical Formulae 1g to 1n.

In Chemical Formulae 1g to 1n,

X₁, X₃, X₄, and Y₁ to Y₁₄ are the same as those defined in ChemicalFormulae 1 and 3.

More specifically, X₁ and X₄ are the same as or different from eachother, and are each independently preferably 0, S or N(Ar₁), and both X₁and X₄ are more preferably N(Ar₁). In this case, a plurality of Ar₁'s isthe same as or different from each other.

Y₁ to Y₄ are the same as or different from each other, and are eachindependently N or C(R₁), and all of Y₁ to Y₄ are preferably C(R₁). Inthis case, a plurality of R₁'s is the same as or different from eachother.

X₃'s are each independently N or C(R₂),

Y₅ to Y₁₄ are the same as or different from each other, and are eachindependently N or C(R₃), and all of Y₅ to Y₁₄ are preferably C(R₃). Inthis case, a plurality of R₃'s is the same as or different from eachother.

Here, Ar₁ and R₁ to R₃ are the same as those defined in ChemicalFormulae 1 and 3.

According to an exemplary embodiment of the present disclosure, it ispreferred that in Chemical Formulae 1a to 1n, X₁ and X₄ are eachindependently N(Ar₁) or S. That is, it is preferred that X₁ is N(Ar₁)and X₄ is S, or X₁ is S and X₄ is N (An), or both X₁ and X₄ are N(Ar₁).

Further, in Chemical Formulae 1a to 1n, Ar₁ is preferably a substitutedor unsubstituted C₆ to C₆₀ aryl group, or a substituted or unsubstitutedheteroaryl group having 5 to 60 nuclear atoms, and Ar₂ to Ar₅ are thesame as or different from each other, and are each independentlypreferably a substituted or unsubstituted C₁ to C₄₀ alkyl group(specifically, a methyl group), or a substituted or unsubstituted C₆ toC₆₀ aryl group (specifically, a phenyl group).

Here, the chemical formulae having a structure in which ChemicalFormulae 1 and 3 are fused include one or more fused azepine moietiesand thus have an electron donor group (EDG) characteristic with a highelectron donor property.

Meanwhile, in the present disclosure, the bipolar compound included as amaterial for the lifetime enhancement layer may include a moiety havingan electron donor group characteristic with a high electron donorproperty, which is represented by the following Chemical Formula 4.

In Chemical Formula 4,

L₁ to L₃ are the same as or different from each other, and are eachindependently selected from the group consisting of a single bond, a C₆to C₆₀ arylene group, and a heteroarylene group having 5 to 60 nuclearatoms,

Ar₆ to Ar₈ are the same as or different from each other, and are eachindependently selected from the group consisting of hydrogen, deuterium,a C₆ to C₄₀ aryl group, and a heteroaryl group having 5 to 40 nuclearatoms, provided that the case where all of Ar₆ to Ar₈ are the same isexcluded,

R₄ to R₆ are the same as or different from each other, and are eachindependently selected from the group consisting of hydrogen, deuterium,a halogen group, a cyano group, a nitro group, an amino group, a C₁ toC₄₀ alkyl group, a C₂ to C₄₀ alkenyl group, a C₂ to C₄₀ alkynyl group, aC₃ to C₄₀ cycloalkyl group, a heterocycloalkyl group having 3 to 40nuclear atoms, a C₆ to C₆₀ aryl group, a heteroaryl group having 5 to 60nuclear atoms, a C₁ to C₄₀ alkyloxy group, a C₆ to C₆₀ aryloxy group, aC₁ to C₄₀ alkylsilyl group, a C₆ to C₆₀ arylsilyl group, a C₁ to C₄₀alkyl boron group, a C₆ to C₆₀ aryl boron group, a C₁ to C₄₀ phosphinegroup, a C₁ to C₄₀ phosphine oxide group, and a C₆ to C₆₀ arylaminegroup,

a to c are each independently an integer of 0 to 3, and

the arylene group, the heteroarylene group, the alkyl group, the alkenylgroup, the alkynyl group, the cycloalkyl group, the heterocycloalkylgroup, the aryl group, the heteroaryl group, the alkyloxy group, thearyloxy group, the alkylsilyl group, the arylsilyl group, the alkylboron group, the aryl boron group, the phosphine group, the phosphineoxide group, and the arylamine group of L₁ to L₃, R₄ to R₆, and Ar₆ toAr₈ are each independently unsubstituted or substituted with one or moreselected from the group consisting of deuterium, a halogen group, acyano group, a nitro group, an amino group, a C₁ to C₄₀ alkyl group, aC₂ to C₄₀ alkenyl group, a C₂ to C₄₀ alkynyl group, a C₃ to C₄₀cycloalkyl group, a heterocycloalkyl group having 3 to 40 nuclear atoms,a C₆ to C₄₀ aryl group, a heteroaryl group having 5 to 40 nuclear atoms,a C₁ to C₄₀ alkyloxy group, a C₆ to C₆₀ aryloxy group, a C₁ to C₄₀alkylsilyl group, a C₆ to C₆₀ arylsilyl group, a C₁ to C₄₀ alkyl borongroup, a C₆ to C₆₀ aryl boron group, a C₁ to C₄₀ phosphine group, a C₁to C₄₀ phosphine oxide group, and a C₆ to C₆₀ arylamine group.

More specifically, it is preferred that in Chemical Formula 4, L₁ to L₃are each independently a single bond, phenylene, biphenylene, orcarbazolylene.

Ar₆ to Ar₈ are the same as or different from each other, and are eachindependently selected from the group consisting of hydrogen, deuterium,a C₆ to C₄₀ aryl group, and a heteroaryl group having 5 to 40 nuclearatoms, and in this case, at least one of Ar₆ to Ar₈ is preferablyselected from a heteroaryl group having 5 to 40 nuclear atoms, whichincludes one or more elements selected from the group consisting of N,O, and S. Provided that the case where all of Ar₆ to Ar₈ are the same isexcluded.

In the present disclosure, in the compounds represented by ChemicalFormulae 1a to 1n and Chemical Formula 4, at least one of R₁ to R₆ andAr₁ to Ar₈ forms a bond with the moiety having an electron withdrawalgroup (EWG) characteristic with a high electron absorption property.

The alkyl in the present disclosure is a monovalent substituent derivedfrom a linear or branched saturated hydrocarbon having 1 to 40 carbonatoms, and examples thereof include methyl, ethyl, propyl, isobutyl,sec-butyl, pentyl, iso-amyl, hexyl, and the like.

The alkenyl in the present disclosure is a monovalent substituentderived from a linear or branched unsaturated hydrocarbon having 2 to 40carbon atoms, which has one or more carbon-carbon double bonds, andexamples thereof include vinyl, allyl, isopropenyl, 2-butenyl, and thelike.

The alkynyl in the present disclosure is a monovalent substituentderived from a linear or branched unsaturated hydrocarbon having 2 to 40carbon atoms, which has one or more carbon-carbon triple bonds, andexamples thereof include ethynyl, 2-propynyl, and the like.

The aryl in the present disclosure means a monovalent substituentderived from an aromatic hydrocarbon having 6 to 60 carbon atoms, whichhas a single ring or a combination of two or more rings. Further, a formin which two or more rings are simply pendant to or fused with eachother may also be included. Examples of the aryl include phenyl,naphthyl, phenanthryl, anthryl, and the like.

The heteroaryl in the present disclosure means a monovalent substituentderived from a monoheterocyclic or polyheterocyclic aromatic hydrocarbonhaving 5 to 60 nuclear atoms. In this case, one or more carbons,preferably 1 to 3 carbons in the ring are substituted with a heteroatomsuch as N, O, S, or Se. Further, a form in which two or more rings aresimply pendant to or fused with each other may also be included, and afused form with an aryl group may also be included. Examples of theheteroaryl include a six-membered monocyclic ring such as pyridyl,pyrazinyl, pyrimidinyl, pyridazinyl, and triazinyl, a polycyclic ringsuch as phenoxathienyl, indolizinyl, indolyl, purinyl, quinolyl,benzothiazole, and carbazolyl, 2-furanyl, N-imidazolyl, 2-isoxazolyl,2-pyridinyl, 2-pyrimidinyl, and the like.

The aryloxy in the present disclosure means a monovalent substituentrepresented by RO—, in which R is an aryl having 6 to 60 carbon atoms.Examples of the aryloxy include phenyloxy, naphthyloxy, diphenyloxy, andthe like.

The alkyloxy in the present disclosure means a monovalent substituentrepresented by R′O—, in which R′ is an alkyl having 1 to 40 carbonatoms, and is interpreted as including a linear, branched, or cyclicstructure. Examples of the alkyloxy include methoxy, ethoxy, n-propoxy,1-propoxy, t-butoxy, n-butoxy, pentoxy, and the like.

The arylamine in the present disclosure means an amine substituted withan aryl having 6 to 60 carbon atoms.

The cycloalkyl in the present disclosure means a monovalent substituentderived from a monocyclic or polycyclic non-aromatic hydrocarbon having3 to 40 carbon atoms. Examples of the cycloalkyl include cyclopropyl,cyclopentyl, cyclohexyl, norbornyl, adamantine, and the like.

The heterocycloalkyl in the present disclosure means a monovalentsubstituent derived from a non-aromatic hydrocarbon having 3 to 40nuclear atoms, and one or more carbons, preferably 1 to 3 carbons in thering are substituted with a hetero atom such as N, O, S, or Se. Examplesof the heterocycloalkyl include morpholine, piperazine, and the like.

The alkylsilyl in the present disclosure is a silyl substituted with analkyl having 1 to 40 carbon atoms, and the arylsilyl means a silylsubstituted with an aryl having 6 to 40 carbon atoms.

The fused ring in the present disclosure means a fused aliphatic ring, afused aromatic ring, a fused heteroaliphatic ring, a fusedheteroaromatic ring, or a combined form thereof.

In the organic electroluminescent device according to the presentdisclosure, the electron transporting layer 305 and the electroninjection layer 306 included in the organic material layer 300 serve totransport electrons injected from the cathode 200 to the light emittinglayer 303.

A material, which constitutes the electron transporting layer 305 andthe electron injection layer 306, is not particularly limited as long asthe material is a material which easily injects electrons and has highelectron mobility, but non-limiting examples thereof include the bipolarcompound, an anthracene derivative, a heteroaromatic compound, an alkalimetal complex compound, and the like.

More specifically, it is preferred that the electron transporting layer305 and/or the electron injection layer 306 of the present disclosureare/is composed of a bipolar material which is the same as the materialconstituting the lifetime enhancement layer 304, that is, the bipolarcompound represented by Chemical Formula 1. Further, for the electrontransporting layer 305 and the electron injection layer 306, it is alsopossible to use a material on which an alkali metal complex compound isco-deposited such that electrons are easily injected from the cathode.In this case, examples of the alkali metal complex compound include analkali metal, an alkali earth metal, or a rare earth metal, and thelike.

The organic material layer 300 of the present disclosure as describedabove may further include an organic film layer (not illustrated) whichblocks electrons and excitons between the hole transporting layer 302and the light emitting layer 303.

The organic film layer has a high LUMO value to block electrons frommoving into the hole transporting layer 302, and has high triplet energyto prevent excitons in the light emitting layer 303 from diffusing intothe hole transporting layer 302. The material, which constitutes theorganic film layer, is not particularly limited, and non-limitingexamples thereof include a carbazole derivative or an arylaminederivative, and the like.

The method for preparing the organic material layer 300 of the presentdisclosure is not particularly limited, but non-limiting examplesthereof include a vacuum deposition method and a solution applicationmethod. Examples of the solution application method include spincoating, dip coating, doctor blading, inkjet printing, a thermaltransfer method, and the like.

The organic electroluminescent device of the present disclosure has astructure in which the anode 100, the organic material layer 300, andthe cathode 200 are sequentially laminated, and may further include aninsulation layer or an adhesive layer between the anode 100 and theorganic material layer 300, or between the cathode 200 and the organicmaterial layer 300. Since the organic electroluminescent device of thepresent disclosure increases the lifetime of the initial brightnesswhile maintaining the maximum light emitting efficiency when voltage,current, or both voltage and current are applied thereto, the lifetimecharacteristics thereof may be excellent.

Hereinafter, the present disclosure will be described in detail throughthe Examples, but the following Examples only exemplify the presentdisclosure, and the present disclosure is not limited by the followingExamples.

[Preparation Examples 1 to 36] Preparation of Compounds LE-01 to LE-36

As the bipolar compound of the present disclosure, compounds representedby the following LE-01 to LE-36 were prepared, ΔEst, triplet energy,ionization potential, E_(HOMO)−E_(LUMO), electron mobility, and holemobility of these compounds were each measured by methods publicly knownin the art, and the results are shown in the following Table 1.

The bipolar compounds LE-01 to LE-36 are each illustrated below.

TABLE 1 Calculated value (B3LYP/6-31G*) Actually measured value BipolarΔEst Triplet Ionization E_(HOMO)- Electron Hole compound (S1-T1) energypotential E_(LUMO) mobility mobility LE-01 0.058 2.39 5.54 3.55 8.9 ×10⁻⁵ 5.5 × 10⁻⁵ LE-02 0.168 2.45 5.50 3.47 5.8 × 10⁻⁵ 3.3 × 10⁻⁵ LE-030.355 2.54 5.71 3.3 8.8 × 10⁻⁴ 1.1 × 10⁻⁵ LE-04 0.059 2.53 5.6 3.37 7.6× 10⁻⁴ 1.2 × 10⁻⁵ LE-05 0.138 2.65 5.58 3.43 7.5 × 10⁻⁴ 9.0 × 10⁻⁵ LE-060.177 2.50 5.64 3.07 9.6 × 10⁻⁴ 9.9 × 10⁻⁵ LE-07 0.121 2.48 5.65 3.429.2 × 10⁻⁴ 9.6 × 10⁻⁵ LE-08 0.298 2.74 6.01 3.33 5.1 × 10⁻⁵ 5.5 × 10⁻⁵LE-09 0.291 2.38 5.71 3.32 9.9 × 10⁻⁴ 2.5 × 10⁻⁵ LE-10 0.321 2.35 5.693.31 1.0 × 10⁻⁵ 6.5 × 10⁻⁵ LE-11 0.261 2.81 6.01 3.36 9.9 × 10⁻⁵ 4.1 ×10⁻⁵ LE-12 0.340 2.78 6.05 3.23 1.1 × 10⁻⁶ 5.4 × 10⁻⁵ LE-13 0.235 2.595.50 3.51 1.3 × 10⁻⁶ 1.1 × 10⁻⁵ LE-14 0.265 2.51 5.51 3.41 2.1 × 10⁻⁶1.6 × 10⁻⁵ LE-15 0.049 2.59 5.56 3.50 7.5 × 10⁻⁵ 5.5 × 10⁻⁵ LE-16 0.0512.54 5.51 3.49 8.5 × 10⁻⁶ 4.5 × 10⁻⁵ LE-17 0.058 2.43 5.64 3.15 7.8 ×10⁻⁵ 5.0 × 10⁻⁵ LE-18 0.074 2.50 5.68 3.24 6.5 × 10⁻⁴ 4.2 × 10⁻⁵ LE-190.082 2.45 5.73 3.20 7.5 × 10⁻⁴ 8.5 × 10⁻⁵ LE-20 0.168 2.56 5.70 3.175.8 × 10⁻⁵ 3.3 × 10⁻⁵ LE-21 0.235 2.48 5.60 3.14 6.4 × 10⁻⁴ 6.1 × 10⁻⁵LE-22 0.129 2.57 5.70 2.93 7.0 × 10⁻⁴ 4.2 × 10⁻⁵ LE-23 0.090 2.53 5.833.54 7.0 × 10⁻⁵ 5.5 × 10⁻⁵ LE-24 0.044 2.47 5.69 3.06 6.6 × 10⁻³ 9.1 ×10⁻⁵ LE-25 0.157 2.43 5.99 3.10 8.1 × 10⁻⁴ 7.9 × 10⁻⁵ LE-26 0.054 2.395.82 3.23 9.5 × 10⁻³ 9.4 × 10⁻⁵ LE-27 0.121 2.41 5.75 3.12 3.7 × 10⁻⁴4.8 × 10⁻⁵ LE-28 0.057 2.50 6.01 3.33 5.1 × 10⁻⁵ 5.5 × 10⁻⁵ LE-29 0.0452.37 6.19 3.36 3.9 × 10⁻⁴ 8.1 × 10⁻⁵ LE-30 0.244 2.45 6.09 3.35 5.6 ×10⁻⁴ 7.5 × 10⁻⁵ LE-31 0.235 2.40 5.70 3.14 6.4 × 10⁻⁴ 6.1 × 10⁻⁵ LE-320.129 2.34 5.68 2.93 7.0 × 10⁻⁴ 4.2 × 10⁻⁵ LE-33 0.342 2.55 6.21 3.237.5 × 10⁻⁴ 5.9 × 10⁻⁵ LE-34 0.295 2.47 6.15 3.06 6.6 × 10⁻³ 9.1 × 10⁻⁵LE-35 0.310 2.43 6.09 3.10 8.1 × 10⁻⁴ 7.9 × 10⁻⁵ LE-36 0.265 2.39 6.183.23 9.5 × 10⁻³ 9.4 × 10⁻⁵ The hole mobility and the electron mobilitywere measured by forming a film having a thickness of 1 μm from thebipolar compound to measure the transit time of the carrier.

[Examples 1 to 36] Manufacture of Blue Fluorescent OrganicElectroluminescent Device

A glass substrate thinly coated with indium tin oxide (ITO) to have athickness of 1,500 Å was ultrasonically washed with distilled water.When the washing with distilled water was completed, the substrate wasultrasonically washed with a solvent such as isopropyl alcohol, acetone,and methanol, dried, transferred to a UV ozone cleaner (Power sonic 405,manufactured by Hwashin Tech), cleaned for 5 minutes by using UV, andthen transferred to a vacuum evaporator.

A device was manufactured by sequentially depositing a hole injectionlayer, a hole transporting layer, a light emitting layer, a lifetimeenhancement layer, an electron transporting layer, an electron injectionlayer, and a cathode in this order on the ITO transparent electrode(substrate) prepared as described above. The structure of themanufactured device is shown in the following Table 2.

TABLE 2 Compound Thickness Hole injection layer DS-205 (Doosan) 80 nmHole transporting layer NPB 15 nm Light emitting layer ADN + 5% DS-405(Doosan) 30 nm Lifetime enhancement layer LE-01 to LE-36 5 nm Electrontransporting layer Alq₃ 25 nm Electron injection layer LiF 1 nm CathodeAl 200 nm

The structures of NPB, AND, and Alq₃ used in Table 2 are as follows.

[Comparative Example 1] Manufacture of Blue Fluorescent OrganicElectroluminescent Device

A device was manufactured in the same manner as in Example 1, exceptthat the electron transporting layer was deposited to have a thicknessof 30 nm without using the lifetime enhancement layer.

[Comparative Example 2] Manufacture of Blue Fluorescent OrganicElectroluminescent Device

A device was manufactured in the same manner as in Example 1, exceptthat BCP having the following structure was used instead of LE-01.

Experimental Example 1

For each of the devices manufactured in Examples 1 to 36 and ComparativeExamples 1 and 2, the driving voltage, the current efficiency, the lightemitting wavelength, and the lifetime (T₉₇) at a current density of 10mA/cm² were measured, and the results are shown in the following Table3.

TABLE 3 Light Driving Current emitting voltage efficiency peak LifetimeCompound (V) (cd/A) (nm) (hr) Example 1 LE-01 4.5 5.9 458 45 Example 2LE-02 4.7 5.6 458 50 Example 3 LE-03 4.5 5.9 458 75 Example 4 LE-04 4.26.0 458 54 Example 5 LE-05 4.1 5.7 458 42 Example 6 LE-06 4.3 6.1 458 78Example 7 LE-07 4.2 6.0 458 75 Example 8 LE-08 4.7 5.7 457 82 Example 9LE-09 4.4 6.1 458 51 Example 10 LE-10 4.1 5.7 458 39 Example 11 LE-114.9 5.4 458 103 Example 12 LE-12 5.0 5.3 457 88 Example 13 LE-13 5.0 5.5458 39 Example 14 LE-14 4.9 5.6 458 40 Example 15 LE-15 4.2 6.1 458 59Example 16 LE-16 4.6 5.7 458 45 Example 17 LE-17 4.5 6.1 458 55 Example18 LE-18 4.3 6.5 458 59 Example 19 LE-19 4.4 6.4 457 60 Example 20 LE-204.7 6.0 458 50 Example 21 LE-21 4.5 6.2 458 75 Example 22 LE-22 4.2 6.6458 55 Example 23 LE-23 4.1 6.6 458 92 Example 24 LE-24 4.4 6.2 457 45Example 25 LE-25 4.3 6.1 458 78 Example 26 LE-26 4.1 6.2 458 64 Example27 LE-27 4.2 6.0 458 75 Example 28 LE-28 4.7 6.4 457 85 Example 29 LE-294.3 6.0 458 62 Example 30 LE-30 4.5 6.3 458 60 Example 31 LE-31 4.6 6.2458 55 Example 32 LE-32 4.5 6.4 457 59 Example 33 LE-33 4.4 6.3 458 81Example 34 LE-34 4.5 6.3 458 70 Example 35 LE-35 4.5 6.3 458 83 Example36 LE-36 4.5 6.2 457 92 Comparative — 4.7 5.6 458 32 Example 1Comparative BCP 5.3 5.9 458 28 Example 2 The lifetime was measured bymeasuring the time when the light emitting luminance became 97% througha lifetime tester.

From the observation of Table 3, it could be confirmed that the organicelectroluminescent devices in Examples 1 to 12, which include thelifetime enhancement layer of the present disclosure, are better thanthe organic electroluminescent devices in Comparative Examples 1 and 2in terms of current efficiency, driving voltage, and lifetime.

[Examples 37 to 51] Manufacture of Green Phosphorescent OrganicElectroluminescent Device

A glass substrate thinly coated with indium tin oxide (ITO) to have athickness of 1,500 Å was ultrasonically washed with distilled water.When the washing with distilled water was completed, the substrate wasultrasonically washed with a solvent such as isopropyl alcohol, acetone,and methanol, dried, transferred to a UV ozone cleaner (Power sonic 405,manufactured by Hwashin Tech), cleaned for 5 minutes by using UV, andthen transferred to a vacuum evaporator.

A device was manufactured by sequentially depositing a hole injectionlayer, a hole transporting layer, a light emitting layer, a lifetimeenhancement layer, an electron transporting layer, an electron injectionlayer, and a cathode in this order on the ITO transparent electrode(substrate) prepared as described above. The structure of themanufactured device is shown in the following Table 4.

TABLE 4 Compound Thickness Hole injection layer m-MTDATA 60 nm Holetransporting layer TCTA 80 nm Light emitting layer CBP + 10% Ir(ppy)₃ 30nm Lifetime enhancement layer See the following Table 5 5 nm Electrontransporting layer Alq₃ 25 nm Electron injection layer LiF 1 nm CathodeAl 200 nm

The structures of m-MTDATA, TCTA, Ir(ppy)₃, and CBP used in Table 4 areas follows.

[Comparative Example 3] Manufacture of Green Phosphorescent OrganicElectroluminescent Device

A device was manufactured in the same manner as in Example 37, exceptthat the electron transporting layer was deposited to have a thicknessof 30 nm without using the lifetime enhancement layer.

[Comparative Example 4] Manufacture of Green Phosphorescent OrganicElectroluminescent Device

A device was manufactured in the same manner as in Example 37, exceptthat BCP used in Comparative Example 2 was used instead of LE-02.

Experimental Example 2

For each of the devices manufactured in Examples 37 to 51 andComparative Examples 3 and 4, the driving voltage, the currentefficiency, the light emitting wavelength, and the lifetime (T₉₇) at acurrent density of 10 mA/cm² were measured, and the results are shown inthe following Table 5.

TABLE 5 Light Driving Current emitting voltage efficiency peak LifetimeCompound (V) (cd/A) (nm) (hr, T₉₇) Example 37 LE-02 7.3 37.0 516 49Example 38 LE-07 7.2 36.9 516 65 Example 39 LE-08 7.4 37.0 517 85Example 40 LE-09 7.1 37.8 516 55 Example 41 LE-10 7.0 35.3 515 54Example 42 LE-11 7.4 36.9 516 98 Example 43 LE-12 7.3 37.1 516 103Example 44 LE-17 7.3 37.0 516 51 Example 45 LE-18 7.1 38.2 516 49Example 46 LE-19 7.2 36.9 516 68 Example 47 LE-22 7.4 37.0 517 59Example 48 LE-23 7.1 40.1 516 95 Example 49 LE-25 7.0 35.3 515 66Example 50 LE-26 7.4 36.9 516 74 Example 51 LE-28 6.8 39.8 516 103Comparative — 7.2 36.8 516 45 Example 3 Comparative BCP 7.9 40.2 516 40Example 4 The lifetime was measured by measuring the time when the lightemitting luminance became 97% through a lifetime tester.

From the observation of Table 5, it could be confirmed that the organicelectroluminescent devices in Examples 37 to 51, which include thelifetime enhancement layer of the present disclosure, are better thanthe organic electroluminescent devices in Comparative Examples 3 and 4in terms of current efficiency, driving voltage, and lifetime.

INDUSTRIAL APPLICABILITY

The present disclosure may provide an organic electroluminescent devicehaving excellent driving voltage, light emitting efficiency, andlifetime by introducing a lifetime enhancement layer, an electrontransporting layer, or an electron injection layer, which is composed ofa bipolar compound having specific physical properties, into the organicelectroluminescent device. Further, a display panel with improvedperformance and lifetime may be provided by applying the organicelectroluminescent device of the present application to a display panel.

The invention claimed is:
 1. An organic electroluminescent devicecomprising: an anode; a cathode; and one or more organic material layersinterposed between the anode and the cathode, wherein said one or moreorganic material layers comprise (a) a light emitting layer comprising ahost material and a dopant material, (b) a lifetime enhancement layercomprising a bipolar compound, (c) an electron transporting layer, and(d) at least one layer selected from the group consisting of a holeinjection layer, a hole transporting layer, and an electron injectionlayer, wherein the lifetime enhancement layer is interposed between thelight emitting layer and the electron transporting layer, wherein thebipolar compound has both an electron withdrawal group (EWG) moiety andan electron donor group (EDG) moiety, and satisfies the following (a) to(d) conditions: (a) an ionization potential [Ip(LEL)] is 5.5 eV or more,(b) E_(HOMO)-E_(LUMO)>2.9 eV, (c) triplet energy is 2.3 eV or more, and(d) ΔEst<0.5 eV (ΔEst indicates a difference between singlet energy andtriplet energy of the compound) wherein the EWG moiety in the bipolarcompound comprises one or more moieties selected from the groupconsisting of the following chemical formulae:

wherein the EDG moiety in the bipolar compound a moiety in which thefollowing Chemical Formula 1 and the following Chemical Formula 3combine with each other to form a fused ring:

in Chemical Formula 1, X₁ is selected from the group consisting of O, S,Se, N(Ar₁), C(Ar₂)(Ar₃), and Si(Ar₄)(Ar₅), Y₁ to Y₄ are the same as ordifferent from each other, and are each independently N or C(R₁), and inthis case, a plurality of R₁'s is the same as or different from eachother, and these groups optionally form a fused ring with an adjacentgroup, X₂ and X₃ are the same as or different from each other, and areeach independently N or C(R₂), and in this case, a plurality of R₂'s isthe same as or different from each other, and these groups optionallyform a fused ring with an adjacent group, R₁ and R₂ and Ar₁ to Ar₅ arethe same as or different from each other, and are each independentlyselected from the group consisting of hydrogen, deuterium, a halogengroup, a cyano group, a nitro group, an amino group, a C₁ to C₄₀ alkylgroup, a C₂ to C₄₀ alkenyl group, a C₂ to C₄₀ alkynyl group, a C₃ to C₄₀cycloalkyl group, a heterocycloalkyl group having 3 to 40 nuclear atoms,a C₆ to C₆₀ aryl group, a heteroaryl group having 5 to 60 nuclear atoms,a C₁ to C₄₀ alkyloxy group, a C₆ to C₆₀ aryloxy group, a C₁ to C₄₀alkylsilyl group, a C₆ to C₆₀ arylsilyl group, a C₁ to C₄₀ alkyl borongroup, a C₆ to C₆₀ aryl boron group, a C₁ to C₄₀ phosphine group, a C₁to C₄₀ phosphine oxide group, and a C₆ to C₆₀ arylamine group, and thealkyl group, the alkenyl group, the alkynyl group, the cycloalkyl group,the heterocycloalkyl group, the aryl group, the heteroaryl group, thealkyloxy group, the aryloxy group, the alkylsilyl group, the arylsilylgroup, the alkyl boron group, the aryl boron group, the phosphine group,the phosphine oxide group, and the arylamine group of R₁ and R₂ and Ar₁to Ar₅ are each independently unsubstituted or substituted with one ormore selected from the group consisting of deuterium, a halogen group, acyano group, a nitro group, an amino group, a C₁ to C₄₀ alkyl group, aC₂ to C₄₀ alkenyl group, a C₂ to C₄₀ alkynyl group, a C₃ to C₄₀cycloalkyl group, a heterocycloalkyl group having 3 to 40 nuclear atoms,a C₆ to C₄₀ aryl group, a heteroaryl group having 5 to 40 nuclear atoms,a C₁ to C₄₀ alkyloxy group, a C₆ to C₆₀ aryloxy group, a C₁ to C₄₀alkylsilyl group, a C₆ to C₆₀ arylsilyl group, a C₁ to C₄₀ alkyl borongroup, a C₆ to C₆₀ aryl boron group, a C₁ to C₄₀ phosphine group, a C₁to C₄₀ phosphine oxide group, and a C₆ to C₆₀ arylamine group,

in Chemical Formula 3, Y₅ to Y₁₄ are the same as or different from eachother, and are each independently N or C(R₃), and in this case, aplurality of R₃'s is the same as or different from each other, and thesegroups optionally form a fused ring with Chemical Formula 1, X₄ isselected from the group consisting of S, Se, N(Ar₁), C(Ar₂)(Ar₃), andSi(Ar₄)(Ar₅), and in this case, a plurality of Ar₁'s to Ar₅'s is thesame as or different from each other, a plurality of R₃ which does notform a fused ring, is the same as or different from each other, and iseach independently selected from the group consisting of hydrogen,deuterium, a halogen group, a cyano group, a nitro group, an aminogroup, a C₁ to C₄₀ alkyl group, a C₂ to C₄₀ alkenyl group, a C₂ to C₄₀alkynyl group, a C₃ to C₄₀ cycloalkyl group, a heterocycloalkyl grouphaving 3 to 40 nuclear atoms, a C₆ to C₆₀ aryl group, a heteroaryl grouphaving 5 to 60 nuclear atoms, a C₁ to C₄₀ alkyloxy group, a C₆ to C₆₀aryloxy group, a C₁ to C₄₀ alkylsilyl group, a C₆ to C₆₀ arylsilylgroup, a C₁ to C₄₀ alkyl boron group, a C₆ to C₆₀ aryl boron group, a C₁to C₄₀ phosphine group, a C₁ to C₄₀ phosphine oxide group, and a C₆ toC₆₀ arylamine group, and the alkyl group, the alkenyl group, the alkynylgroup, the cycloalkyl group, the heterocycloalkyl group, the aryl group,the heteroaryl group, the alkyloxy group, the aryloxy group, thealkylsilyl group, the arylsilyl group, the alkyl boron group, the arylboron group, the phosphine group, the phosphine oxide group, and thearylamine group of R₃ are each independently unsubstituted orsubstituted with one or more selected from the group consisting ofdeuterium, a halogen group, a cyano group, a nitro group, an aminogroup, a C₁ to C₄₀ alkyl group, a C₂ to C₄₀ alkenyl group, a C₂ to C₄₀alkynyl group, a C₃ to C₄₀ cycloalkyl group, a heterocycloalkyl grouphaving 3 to 40 nuclear atoms, a C₆ to C₄₀ aryl group, a heteroaryl grouphaving 5 to 40 nuclear atoms, a C₁ to C₄₀ alkyloxy group, a C₆ to C₆₀aryloxy group, a C₁ to C₄₀ alkylsilyl group, a C₆ to C₆₀ arylsilylgroup, a C₁ to C₄₀ alkyl boron group, a C₆ to C₆₀ aryl boron group, a C₁to C₄₀ phosphine group, a C₁ to C₄₀ phosphine oxide group, and a C₆ toC₆₀ arylamine group.
 2. The organic electroluminescent device of claim1, wherein the light emitting layer is a blue fluorescence, a greenfluorescence, or a red phosphorescence.
 3. The organicelectroluminescent device of claim 1, wherein when the light emittinglayer is a green phosphorescence, the bipolar compound comprised in thelifetime enhancement layer has triplet energy of 2.3 eV or more and anionization potential of 6.0 eV or more.
 4. The organicelectroluminescent device of claim 1, wherein when the light emittinglayer is a blue phosphorescence, the bipolar compound comprised in thelifetime enhancement layer has triplet energy of 2.7 eV or more and anionization potential of 6.0 eV or more.
 5. The organicelectroluminescent device of claim 1, wherein a material for theelectron transporting layer is the same as a material for the lifetimeenhancement layer.
 6. The organic electroluminescent device of claim 1,wherein a material for the electron injection layer is the same as amaterial for the lifetime enhancement layer.
 7. The organicelectroluminescent device of claim 1, wherein the electron injectionlayer or the electron transporting layer is provided by co-depositingalkali metal complexes.
 8. The organic electroluminescent device ofclaim 1, wherein an organic film layer blocking electrons and excitonsis further provided between the hole transporting layer and the lightemitting layer.
 9. The organic electroluminescent device of claim 1,wherein the light emitting layer comprises the dopant in a range of 0.1wt % to 30 wt %.
 10. The organic electroluminescent device of claim 1,wherein a plurality of light emitting layers is sequentially laminatedbetween the hole transporting layer and the electron transporting layerto implement a mixed color when voltage or current is applied thereto.11. The organic electroluminescent device of claim 1, wherein betweenthe hole transporting layer and the electron transporting layer, aplurality of light emitting layers composed of homogeneous material islaminated, or a plurality of light emitting layers composed ofheterogeneous materials is provided in series to implement a mixed colorwhen voltage or current is applied thereto.
 12. An organicelectroluminescent device comprising: an anode; a cathode; and one ormore organic material layers interposed between the anode and thecathode, wherein said one or more organic material layers comprise (a) alight emitting layer comprising a host material and a dopant material,(b) a lifetime enhancement layer comprising a bipolar compound, (c) anelectron transporting layer, and (d) at least one layer selected fromthe group consisting of a hole injection layer, a hole transportinglayer, and an electron injection layer, wherein the lifetime enhancementlayer is interposed between the light emitting layer and the electrontransporting layer, wherein the bipolar compound has both an electronwithdrawal group (EWG) moiety and an electron donor group (EDG) moiety,and satisfies the following (a) to (d) conditions: (a) an ionizationpotential [Ip(LEL)] is 5.5 eV or more, (b) E_(HOMO)-E_(LUMO)>2.9 eV, (c)triplet energy is 2.3 eV or more, and (d) ΔEst<0.5 eV (ΔEst indicates adifference between singlet energy and triplet energy of the compound)wherein the EWG moiety in the bipolar compound comprises one or moremoieties selected from the group consisting of the following chemicalformulae:

wherein the EDG moiety in the bipolar compound comprises a moietyrepresented by the following Chemical Formula 1g:

in Chemical Formula 1g, X₁ and X₄ are the same as or different from eachother, and each independently are selected from the group consisting ofO, S, Se, N(Ar₁), C(Ar₂)(Ar₃), and Si(Ar₄)(Ar₅), and in this case, aplurality of Ar₁'s to Ar₅'s is the same as or different from each other,Y₁ to Y₄ are the same as or different from each other, and are eachindependently N or C(R₁), and in this case, a plurality of R₁'s is thesame as or different from each other, and these groups optionally form afused ring with an adjacent group, Y₅ to Y₈, and Y₁₁ to Y₁₄ are the sameas or different from each other, and are each independently N or C(R₃),and in this case, a plurality of R₃'s is the same as or different fromeach other, R₁, R₃ and Ar₁ to Ar₅ are the same as or different from eachother, and are each independently selected from the group consisting ofhydrogen, deuterium, a halogen group, a cyano group, a nitro group, anamino group, a C₁ to C₄₀ alkyl group, a C₂ to C₄₀ alkenyl group, a C₂ toC₄₀ alkynyl group, a C₃ to C₄₀ cycloalkyl group, a heterocycloalkylgroup having 3 to 40 nuclear atoms, a C₆ to C₆₀ aryl group, a heteroarylgroup having 5 to 60 nuclear atoms, a C₁ to C₄₀ alkyloxy group, a C₆ toC₆₀ aryloxy group, a C₁ to C₄₀ alkylsilyl group, a C₆ to C₆₀ arylsilylgroup, a C₁ to C₄₀ alkyl boron group, a C₆ to C₆₀ aryl boron group, a C₁to C₄₀ phosphine group, a C₁ to C₄₀ phosphine oxide group, and a C₆ toC₆₀ arylamine group, and the alkyl group, the alkenyl group, the alkynylgroup, the cycloalkyl group, the heterocycloalkyl group, the aryl group,the heteroaryl group, the alkyloxy group, the aryloxy group, thealkylsilyl group, the arylsilyl group, the alkyl boron group, the arylboron group, the phosphine group, the phosphine oxide group, and thearylamine group of R₁ and R₃ and Ar₁ to Ar₅ are each independentlyunsubstituted or substituted with one or more selected from the groupconsisting of deuterium, a halogen group, a cyano group, a nitro group,an amino group, a C₁ to C₄₀ alkyl group, a C₂ to C₄₀ alkenyl group, a C₂to C₄₀ alkynyl group, a C₃ to C₄₀ cycloalkyl group, a heterocycloalkylgroup having 3 to 40 nuclear atoms, a C₆ to C₄₀ aryl group, a heteroarylgroup having 5 to 40 nuclear atoms, a C₁ to C₄₀ alkyloxy group, a C₆ toC₆₀ aryloxy group, a C₁ to C₄₀ alkylsilyl group, a C₆ to C₆₀ arylsilylgroup, a C₁ to C₄₀ alkyl boron group, a C₆ to C₆₀ aryl boron group, a C₁to C₄₀ phosphine group, a C₁ to C₄₀ phosphine oxide group, and a C₆ toC₆₀ arylamine group.